1. Field of the Invention
This invention relates generally to a medical valve, and in particular to a positive flow valve which, when connected between a medical implement and a catheter to facilitate fluid flow therethrough, induces a positive flow of fluid through a tip of the catheter from the valve upon disconnection of the medical implement, thereby eliminating the problem of blood-clogging or clotting in the catheter.
2. Description of the Related Art
The manipulation of fluids for parenteral administration in hospitals and medical settings routinely involves the use of connectors and valves for facilitating the movement of fluids between two points. Fluid connectors and valves typically employ needles or luers to pierce a septum or seal covering sterile tubing or to pierce a septum or seal of a medicament container of fluid. Fluid then passes from the container or fluid-filled tubing into a syringe or second set of tubing. Since the ready passage of fluids through the connectors and valves is often critical to patient survival, it is imperative that the connectors and valves function reliably and repeatedly. Connectors and valves that malfunction during use may be life-threatening.
Many connectors or valves, especially those employing several mechanical components, have a relatively high volume of fluid space within them. There is potential for the creation of a “dead space” (i.e. an increase in the fluid containment area which will cause fluid within the patient to be drawn therein) in the fluid space during removal or disconnection of the tubing or other medical implements such as conduits, syringes, IV sets (both peripheral and central lines), piggyback lines, and similar components which can be used in connection with a medical valve. Withdrawal of the medical implement creates a suction force which draws fluid back toward the valve in a phenomenon known as “backflash.” This is particularly troublesome in the case where the valve is connected through a catheter to a patient. A suction force is generated by the withdrawal of the medical implement which draws blood from the patient into the catheter. This blood clot and clog the catheter near its tip, rendering it inoperable, and may even result in a clot of blood in the patient, which may prove fatal. Attempts to avoid backflash by coating the inner surface of the catheter near its tip in order to prevent blood from sticking to the interior surfaces of the catheter and clogging it have not been successful.
The risk of blood clogging of the catheter is significantly heightened where the inner diameter of the catheter is small (e.g., 27 gauge). These small catheters have the advantage, however, that they reduce the trauma and discomfort caused by insertion into a patient. Because these catheters have a very small passage therethrough, even a small suction force may draw sufficient amount of fluid back through a catheter toward the valve to introduce blood into the catheter tip, which blood may clog the catheter's passage. This back flow is hereinafter referred to as a negative flow. FIG. 1 shows an example of a catheter 50 having a small portion near the tip 52 that is inserted into the patient, and a valve 54 connected between one end of the catheter and a medical implement 56. The problem associated with the creation of “dead space” or a drawing of fluid from the catheter towards the valve is illustrated by this Figure. As illustrated therein, when the tip or nose of the medical implement 56 is withdrawn from the valve 54, the space previously occupied by the implement 56 becomes “dead space.” This newly created space has a lower pressure than the fluid within the valve, catheter and patient, such that fluid is drawn into that space, and thus travels from the patient in the direction of the dead space. To avoid blood from being drawn into the catheter, a zero flow or a positive flow, defined as flow or fluid displacement directed from the valve through the catheter tip to the patient, must be effected at the time the medical implement is withdrawn. For a sufficient margin of safety, a positive flow toward the patient is desirable.
To avoid negative flow or backflash, healthcare workers presently practice the method of disconnecting the valve and simultaneously transferring fluid through the catheter by manipulating the medical implement to induce positive flow. This method is clumsy and difficult, and may result in an inaccurate transfer of medicament.
One way to induce a positive flow in the catheter is illustrated in FIGS. 2a and 2b. Here, the proximal end of a valve 180 is enclosed with a stylet or displacer 182 upon withdrawal of the medical implement (not shown). An elongated portion 184 of the stylet 182 takes up at least a portion of the fluid space, thereby reducing the volume of the fluid space, and may eliminate the dead space therein. The elongated portion 184, however, must be sufficiently long to displace more fluid than that volume of fluid which may be drawn from the catheter towards the valve by the withdrawal of the implement, and hence may be difficult to construct for proper performance. The use of the stylet 182 further requires an additional step that may be overlooked by the nurse and the stylet 182 may be misplaced or lost. In addition, this specific type of valve 180 has many significant drawbacks, among them the fact that it does not have a seal with a swabbable surface that can be swabbed after each use for sterility.